This invention relates to a sintered body having a high corrosion resistance and containing ZrB.sub.2.
The sintered bodies containing ZrB .sub.2 have been studied and investigated for a long time and a number of patent aplications have been made on this subject. However, the known sintered bodies have not been found extensively to be commercially useful. For obtaining a sintered body containing ZrB.sub.2, it is known to add silicates such as MoSi.sub.2 or ZrSi.sub.2, carbides such as SiC, B.sub.4 C or WC, nitrides such as TaN, BN, AlN or HfN, oxides such as ZrO.sub.2 and metal powders as a sintering aid or additional components to ZrB.sub.2 and to sinter the resulting mixture For obtaining a sintered body containing ZrB.sub.2 and TiB.sub.2, metal powders and tungsten carbide base super hard alloys may be used as a sintering aid, as disclosed in Japanese Laid-open Pat. Publication No. 44768/1986.
However, when the silicates such as MoSi.sub.2 or ZrSi.sub.2 or metal powders are used as the sintering aids, the resulting hard alloy is inferior in strength, corrosion resistance and anti-oxidation due to its tendency towards melting and decomposition under elevated temperatures. Although nitrides in general are superior in hardness and strength, these lack in anti-oxidation properties, corrosion resistance and thermal impact resistance. ZrO.sub.2, mentioned herein as the oxide, is not satisfactory in anti-oxidation properties, while it is also poor in strength when used under elevated temperatures and under an oxidizing atmosphere due to transition from the tetragonal to the monoclinical system or vice versa. SiC, B.sub.4 C or WC, used as the carbides, apparently are insufficient in oxidation resistance.
These sintering aids have several deficiencies, as discussed hereinabove, and cannot be practically employed in a form taking advantage of the strong points of ZrB.sub.2 and TiB.sub.2.